a(n) = ( n*(n + 1)*(2*n + 1)/6 )^2.

Terms

a(0) =0a(1) =1a(2) =25a(3) =196a(4) =900a(5) =3025a(6) =8281a(7) =19600a(8) =41616a(9) =81225a(10) =148225a(11) =256036a(12) =422500a(13) =670761a(14) =1030225a(15) =1537600a(16) =2238016a(17) =3186225a(18) =4447881a(19) =6100900a(20) =8236900a(21) =10962721a(22) =14402025a(23) =18696976a(24) =24010000a(25) =30525625a(26) =38452401a(27) =48024900a(28) =59505796a(29) =73188025